Topics covered in this episode:

httpxyz one month in
Learn concurrency - a deep dive into multithreading with Python
pip 26.1 - lockfiles and dependency cooldowns
Python 3.15 sentinal values from PEP 661
Extras
Joke

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Michael #1: httpxyz one month in

First version of httpxyz contained just the fixes to get zstd working, and the fixes to get the test suite running on python 3.14, some ‘housekeeping’ changes related to the renaming
End of March: a compatibility shim that allows you to use httpxyz even with third-party packages that import httpx themselves, as long as you import httpxyz first.
- Importing httpxyz automatically registers it under the httpx name in sys.modules , see https://httpxyz.org/httpx-compatibility/
Fixed a WHOLE bunch of performance related issues by forking httpcore

Brian #2: Learn concurrency - a deep dive into multithreading with Python

Nikos Vaggalis
“Whenever you are trying to speed up code using multiple cores, always ask yourself: “Do these threads need to talk to each other right now?” If the answer is yes, it will be slow. The best parallel code splits a big job into completely isolated chunks, processes them separately, and merges the results at the finish line.”
Good overview of thread concurrency with Python and how that’s been improved dramatically with free-threaded Python
Defines lots of terms you come across, including “embarrassingly parallel multithreading”
There’s a counter example that’s nice
- Start with a shared resource, a counter, and multiple threads updating it
- Attempt to fix with threading.Lock(), which fixes it, but slows things down
- Good explanation of why
- Proper fix with concurrent.futures and separating the work of different threads so that they can be independent and their results can be combined when they’re all finished.

Michael #3: pip 26.1 - lockfiles and dependency cooldowns

Python 3.9 is no longer supported
Experimental: installing from pylock files
Dependency cooldowns (see my post about this)
Lifting several 2020 resolver limitations

Brian #4: Python 3.15 sentinal values from PEP 661

MISSING = sentinel("MISSING")
def next_value(default: int | MISSING = MISSING):
    ...
    if default is MISSING:
       ...

Take a name str as a constructor parameter
Intended to be compared with is operator, similar to None
Sentinal objects can be used as a type, also similar to None
- and can be combined with other types with |.
Unlike None, sentinal values are truthy. (Elipses ... are also truthy)
- This seems like a strange choice. but I guess it must have made sense to someone.
- It does force you to use is instead of depending on False-ness, so I guess it’ll make code using sentinels more readable.
Interesting that the PEP was started in 2021, and we’re finally getting it this year.

Extras

Brian:

Before GitHub - Armin Ronacher
tenacity - cross-platform multi-track audio editor/recorder
- learned about it from Armin’s article

Joke:

Joke option Make it myself
- Seems similar to what people think about software now

Links

#479 Talking About Types

Python Bytes